1. Field of the Invention
The present invention relates to nonwoven fabric webs. More particularly, this invention relates to antimicrobially-active nonwoven webs, to methods for making such webs, and to wet wipers containing such webs.
Wet wiper products should have antimicrobial properties in order to destroy or inhibit the growth of various microorganisms, including bacteria, yeasts, and molds, whose growth is promoted by the moist conditions prevailing in said products. There are at least four approaches that have been used to obtain some type of antimicrobial protection in wet wiper products: substrate pore size control; sterilization; chemical surface treatment; and chemical saturation.
2. Description of the Prior Art
The primary method of antimicrobial control and protection currently used in wet wiper products is that which is achieved by a chemical permeation of preservative agents throughout the wet wiper product. This permeation may be achieved by padding the wiper fabric during its manufacture and/or by incorporating the chemicals in the liquid or lotion phase of the wiper product. Padding the fabric is generally not favored as a commercial technique, however, because of the additional manufacturing processing costs associated therewith. Since a liquid or lotion must be applied to the fabric in a wet wiper product in any event, and since the liquid or lotion without antimicrobial control or preservation agents would present a prime opportunity for microbiological growth, a preferred method of applying the chemical preservation or antimicrobial control has been to incorporate soluble preservative agents in the lotion phase and then associate the preserved lotion with the fabric. In both of these permeation scenarios, the end result is the same. Since the preservatives and antimicrobial agents are soluble in the liquid or lotion phase, they ultimately equilibrate through the wet wiper product and provide a homogeneous chemical method of antimicrobial control. When a wet wiper product of this type is used by the consumer, the antimicrobial agents from the liquid or lotion phase remain behind on the user's skin. Many individuals exhibit adverse reactions to such preservatives. Hence consumer use of the wet wiper product is significantly impeded. Both insolubility and antimicrobial-spectrum-activity considerations significantly limit the use of hypoallergenic preservatives in the liquid wetting solution.
U.S. Pat. No. 4,615,937 teaches a means for incorporating the antimicrobial properties required in the wet wiper product in a manner substantive to and within the wet wiper fabric. The issues of solubility and antimicrobial-activity-spectrum are overcome because no harmful residue is left on the skin of the user. In addition, the increased costs of padding the wet wiper fabric during its manufacturing process can be avoided by incorporating these substantive antimicrobials into the synthetic bonding agent typically already required for such nonwoven fabrics.
In the wet wipe system described in U.S. Pat. No. 4,615,937, however, the antimicrobial agent renders the substrate hydrophobic and needed absorbency properties are lost. To remedy this, a wetting agent can be incorporated into the fabric. Wetting agents, however, may restore only a portion of the original absorbency qualities of the fabric. Furthermore, while appropriate wetting agents are suitable for most applications, it would be desirable for some uses--for example in burn and wound management--to simplify the chemical additive system employed by eliminating these compounds.